I don't know if I'd say this is a great card vs aggro; most of the time I would silence something like Tazdingo or Belcher with an Ironbeak Owl. Since this isn't immune to battlecries, it doesn't seem particularly valuable in that role. It also is killed by Stampeding Kodo, unlike its alternatives.

Where I really think it has value is in a control deck late game. It can't be removed by spells, so when you drop it your opponent has a few options

1) Attack it with small minions, who will either be killed or weakened enough to become susceptible to AOE

2) Attack it with a large minion, meaning that you get better initiative with your large minions during the next turn's trades (for instance, if they attack it with a giant, that's one giant who now has 6 health and isn't able to kill one of your beefy minions this turn).

All in all, not an amazing card. But fairly useful for 4 mana, and definitely more useful the less minions your opponent has on the board. The fewer options your opponent has for attacking, the better trades you will get.

It's confusing why people are comparing this to Sen'jin. This is supieror due to that mech synergy.

Sen'Jin is so strong because it kills every card that comes before it (at least against aggro). This card can't deal with 3-health minions as well, and it curves nicely into a Stampeding Kodo or, god forbid, Coin + Cabal Shadow Priest

It's confusing why people are comparing this to Sen'jin. This is supieror due to that mech synergy.

Sen'Jin is so strong because it kills every card that comes before it (at least against aggro). This card can't deal with 3-health minions as well, and it curves nicely into a Stampeding Kodo or, god forbid, Coin + Cabal Shadow Priest

But like I said with the mech synergy with the cards that +2/+2 it, you get a 4/7 spell/hero power immune taunt. Even if it takes a silence thats a silence away from another one of your big guys.

If you use Sen'jin Shieldmasta to survive against aggro, this card is strictly better, because it is guaranteed (well, except for silence) that your opponent needs to trade into it, and most aggro minions have 1 or 2 health.